Mr. Caretaker,
I've been using Waterfed Poles (ours is the Reach & Wash) for coming up 4 years. We have a lot of contracts with it and have not lost one over the use of the system. It appears at first to be window cleaning on a stick, but there is a learning curve, also the building has to get used to being cleaned this way, 3 cleans before good results in some cases. The reason for this is the frames have to be flushed clean and old soap removed. And it has to be cleaned this way regularly.
We have invested in window cleaning this way not because we like spending thousands of pounds (they are not cheap) but because of Health & Safety legislation. YOU or your boss as building owners are responsible for the safety of any workers that work on site and as such can be sued in court and made to conform to standards by the Health & Safety Executive. Inspectors now make regular visits to sites.
Now there are some windows that do not clean as well with the system. Paintwork in poor repair or badly done, some glass that repels water so the water doesn't rinse properly, window in a high dust area etc or too infrequent cleanings are all a problem. Some can be overcome, some not. How often are the windows cleaned? If it's 6 monthly this could be the problem.
If the results are consistantly poor the other option is a Mobile Work Platform or Cherry Picker. This would mean the glass would get done by hand as required and you would conform with Health & Safety. Although a more costly option it's not that expensive, especially as I suspect you are having, infrequently.
By the way, current Health & Safety legislation for ladder use is up to 6 meters unsecured, 6 to 9 meters secured by means of stabiliser or eyebolts (you could have these installed but at your cost and load tested with a certificate once a year) above 9 meters Cherry Picker or Scaffolding.
If you require any more information on this telephone the National Federation Of Master Window & General Cleaners on 0161 432 8754, they are very helpful, I am on the board.